It is well known in the hydraulic pump and motor art that certain types of hydraulic units have rotary elements which are in contact with the working fluid and wherein the capacity of the unit is proportional to the axial width of the unit. Such units include the vane type, the roller vane type, gearing units, gear type and gerotor type, among others. One example of such hydraulic unit is McKittrick U.S. Pat. No. 3,373,693 issued Mar. 19, 1968. It is also recognized in the hydrostatic transmission art that a fluid pumping unit of one type can be connected in fluid communication with a hydraulic motor unit of either the same type or another type so that the rotary input to the pump causes fluid flow to the motor to provide a rotary output. Quite often in hydrostatic transmissions, the pump and motor are in separate housings such as taught in Musick et al. U.S. Pat. No. 2,307,851 issued Jan. 12, 1943. It is also well known in hydrostatic transmissions to have the pump and motor housings abut each other so as to eliminate the need for external hoses or other fluid communication means between the two housings. Brown et al. U.S. Pat. No. 3,751,924 issued Aug. 14, 1973 and Costomski U.S. Pat. No. 3,996,841 issued Dec. 14, 1976 teach examples of such pump and motor combinations.